U.S. patent number 5,225,946 [Application Number 07/478,389] was granted by the patent office on 1993-07-06 for information recording/reproducing apparatus for reproducing a portion of a picture signal during a fast feeding/rewinding operation.
This patent grant is currently assigned to Pioneer Electronic Corporation. Invention is credited to Satoshi Uchiumi.
United States Patent |
5,225,946 |
Uchiumi |
July 6, 1993 |
Information recording/reproducing apparatus for reproducing a
portion of a picture signal during a fast feeding/rewinding
operation
Abstract
A rotary video head type information recording/reproducing
apparatus in which a video tape runs while being in contact with a
stationary head at the time of fast-feeding/rewinding of the video
tape. In recording/reproducing operation of the information
recording/reproducing apparatus, a one-scene picture is extracted
at intervals of a predetermined period from a picture signal and
the extracted picture is recorded on the video tape by the
stationary head in synchronism with the picture signal. When it is
desired to perform a picture search, a still picture which changes
at intervals of the predetermined period can be reproduced on a
picture screen of a display only by performing the
fast-feeding/rewinding operation. Accordingly, an operator can
perform search for a desired picture at a high speed by referring
to the timing of change of the still picture actually displayed on
the picture screen.
Inventors: |
Uchiumi; Satoshi (Saitama,
JP) |
Assignee: |
Pioneer Electronic Corporation
(Tokyo, JP)
|
Family
ID: |
12557986 |
Appl.
No.: |
07/478,389 |
Filed: |
February 12, 1990 |
Foreign Application Priority Data
|
|
|
|
|
Feb 20, 1989 [JP] |
|
|
1-39614 |
|
Current U.S.
Class: |
360/72.1;
386/208; 386/241; 386/316; 386/342; 386/349; 386/E5.024;
G9B/15.002; G9B/15.03; G9B/27.013; G9B/27.02; G9B/27.045;
G9B/27.047 |
Current CPC
Class: |
G11B
15/02 (20130101); G11B 15/1875 (20130101); G11B
27/036 (20130101); G11B 27/107 (20130101); G11B
27/324 (20130101); H04N 5/9205 (20130101); G11B
27/326 (20130101); H04N 5/9261 (20130101); G11B
2220/90 (20130101); G11B 2220/91 (20130101); H04N
5/783 (20130101) |
Current International
Class: |
G11B
15/18 (20060101); G11B 15/02 (20060101); G11B
27/32 (20060101); G11B 27/10 (20060101); G11B
27/031 (20060101); G11B 27/036 (20060101); H04N
5/92 (20060101); H04N 5/926 (20060101); H04N
5/783 (20060101); G11B 015/18 () |
Field of
Search: |
;360/10.3,14.1,14.2,72.1,72.2,33.1,35.1 ;358/310,311,312,335 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Sniezek; Andrew L.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak &
Seas
Claims
What is claimed is:
1. A rotary video head type information recording/reproducing
apparatus, for recording and reproducing a picture signal, in which
a video tape runs while being in contact with a stationary head at
a high speed so as to allow video searching of a portion of said
picture signal during a fast-feeding/rewinding operation of said
video tape relative to the speed of the tape while in contact with
a recording/reproducing head during a recording/reproducing
operation, said apparatus comprising:
a read/write memory for periodically storing at least one portion
of said picture signal;
a recording control circuit for periodically recording said at
least one portion of said picture signal on said video tape through
said stationary head during said recording/reproducing operation;
and
a reproducing control circuit for reproducing said periodic
recorded at least one portion from said video tape through said
stationary head and for outputting said at least one portion during
video searching as said recording/reproducing apparatus is
performing a fast-feeding/rewinding operation, wherein during the
fast-feeding/rewinding operation said recording/reproducing head is
not in contact with said video tape.
2. An information recording/reproducing apparatus according to
claim 1, in which said at least one portion reproduced through said
stationary head is output by said reproducing control circuit in
the form of a reduced-scale picture signal relative to the scale of
the picture signal output during a recording/reproducing
operation.
3. An information recording/reproducing apparatus according to
claim 2, in which said at least one portion output from said
reproducing control circuit is representative of said picture
signal appearing on a portion of said video tape that would be in
contact with a recording/reproducing head of the apparatus during a
recording/reproducing operation.
4. An information recording/reproducing apparatus according to
claim 3, in which said recording control circuit writes in said
memory directly at least a portion of a picture signal immediately
before the operation of said information recording/reproducing
apparatus changes from a recording into a recording pause or stop
operation, and writes in said memory at least a portion of a
picture signal immediately before the operation of said information
recording/reproducing apparatus changes from a reproducing
operation to a stop operation.
5. An information recording/reproducing apparatus according to
claim 4, in which said reproducing control circuit outputs said
recording picture signal or reproducing picture signal immediately
before the operation of said information recording/reproducing
apparatus changes, when said information recording/reproducing
apparatus is in the state of recording pause or stop.
6. An information recording/reproducing apparatus according to
claim 2, in which said recording control circuit writes in said
memory directly at least a portion of a picture signal immediately
before the operation of said information recording/reproducing
apparatus changes from a recording into a recording pause or stop
operation, and writes in said memory at least a portion of a
picture signal immediately before the operation of said information
recording/reproducing apparatus changes from a reproducing
operation to a stop operation.
7. An information recording/reproducing apparatus according to
claim 6, in which said reproducing control circuit outputs said
recording picture signal or reproducing picture signal immediately
before the operation of said information recording/reproducing
apparatus changes, when said information information
recording/reproducing apparatus is in the state of recording pause
or stop.
8. An information recording/reproducing apparatus according to
claim 1, in which said recording control circuit writes in said
memory directly at least a portion of a picture signal immediately
before the operation of said information recording/reproducing
apparatus changes from a recording operation into a recording pause
or stop operation, and writes in said memory at least a portion of
a picture signal immediately before the operation of said
information recording/reproducing apparatus changes from a
reproducing operation to a stop operation.
9. An information recording/reproducing apparatus according to
claim 8, in which said reproducing control circuit outputs said
recording picture signal or reproducing picture signal immediately
before the operation of said information recording/reproducing
apparatus changes, when said information recording/reproducing
apparatus is in the state of recording pause or stop.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an information
recording/reproducing apparatus such as a video tape recorder
(hereinafter abbreviated as "VTR"), and more particularly, relates
to an information recording/reproducing apparatus suitable for
video searching (hereinafter abbreviated as "SEARCH") in the fast
feeding (hereinafter abbreviated as "FF") or rewinding (hereinafter
abbreviated as "REW") of a magnetic recording medium (hereinafter
referred to as "video tape").
VTRs use long and continuous video tapes as a recording medium, so
that recording can be continued for a long time of 6 hours or more.
However, VTRs have a problem that a long time is required for
searching a desired scene recorded on the video tape and that the
exact position of the scene cannot be found easily. The problem is
caused by the fact that recording information is recorded on a
video tape serially in the direction of running of the video tape
on the whole. Accordingly, the video tape must be fed till the
desired scene appears. In such VTRs, main examples of searching
systems which have been put into practice are (1) a tape counter
system, (2) a cue review system, and (3) an index/address system.
In the following, the respective systems are described in
brief.
[1] Tape Counter System
This system comprises counting the quantity of running of a video
tape by a counter to indicate the count value of the counter as the
quantity of time. An operator feeds rapidly or rewinds the video
tape by reference to the indicated count value to search a desired
scene.
However, the time indicated by the count value is relative time on
the tape though the indication has been improved in recent years to
obtain information of hour, minute and second. Accordingly, a
series of procedures of rewinding the tape to the top thereof once,
resetting the counter, memorizing the count value of the counter at
the position of the starting of the desired program and feeding the
tape rapidly to the position of the starting of the desired program
is required.
[2] Cue Review System
This system comprises reproducing a picture while making the video
tape running at a relatively high speed in a state where the tape
is wound on a rotary drum to thereby search a desired reproduction
scene.
However, the rotation number of the rotary drum (that is, the
vertical synchronizing period of the reproducing video signal) must
be deviated in order to keep the speed of the tape almost constant
relative to a rotary head. Accordingly, the speed of the tape is
limited to secure the synchronism of a television receiver set.
Though the system is convenient for skipping a relatively short
portion such as a commercial message portion or the like, a long
time is required for searching a long distance. For example, in the
case where the deviation of the vertical synchronizing period is
limited within the range of .+-.5% in variable-speed reproduction
of the video tape recorded in the VHS-type standard mode, the
searching speed is limited to an about 9-fold speed. In practice,
the time of 13 minutes or more is required for searching the whole
of the tape having the capacity of 2 hours. Further, repeating the
high-speed running of the video tape in the state where the tape is
wound on the rotary drum, causes deposition of magnetic powder of
the video tape on the video head.
[3] Index/Address System
This system uses a control signal (hereinafter referred to as "CTL
signal") for reproduction tracking. In short, in the case of the
VHS type, the index for marking or the address for addressing can
be superposed on the CTL signal by giving a change to the duty
ratio of the CTL signal. Therefore, the high-seed searching of the
2-hour tape is finished in about 3 minutes by constituting the tape
running mechanism so that the tape runs in a state where the tape
is in contact with the CTL stationary head at the time of
FF/REW.
Although this system has an advantage in that searching can be made
based on a numerical value simpler than that of the tape counter
system (1), the index expresses merely the relative address between
picture informations and the address expresses merely the value of
absolute address. Accordingly, what scene is recorded at the
position cannot be known. Accordingly, to know the obvious
correlation between the index/address and the picture, a note
described by the operator or the memory of the operator is
required.
In general, the index is used to be marked only at the time of the
starting of a television program, for example, at the point of the
starting of recording. As a result, only one index is marked
automatically in the top portion (hereinafter referred to as "tape
top") of the video tape in the case where a long-hour television
program is recorded. If a new index is not marked by a manual
operation, the function of the index is no good use. If an index is
marked at a suitable position, a scene to be searched must be
designated by a numerical value (address) with no correlation with
a picture. Accordingly, a sense of irrelevancy on the operation is
not yet eliminated. To improve the disadvantage, the following
applied example has been proposed. [3-1] Index Scanning Reproducing
System
According to this system, high-speed searching of an index is
performed while performing high-speed running of the video tape
through the FF/REW operation, the tape running mechanism is
switched to the reproducing mode to obtain an ordinary running
speed when the index is detected, and a picture is reproduced only
for several seconds to search the picture exactly corresponding to
the index. Then, after the reproduction for several seconds, the
apparatus is switched again to the "FF/REW" mode to search the next
index.
However, this system has a disadvantage in that the switching
operation of the tape running mechanism is required to reduce the
searching speed because the tape running mechanism is switched in
the course of searching. [3-2] Multi-Index Systems
According to this system, scale-down scenes are formed from
pictures at the respective positions where multiple index data are
marked, and multi-screen data (for example, 4.times.4=16 screens)
are produced to make it possible to reproduce the scale-down scenes
simultaneously on one CRT display. When the tape top portion is
reproduced at the time of reproducing after the multi-screen data
thus produced are after-recorded in the tape top portion, index
data contained in the video tape and pictures corresponding to the
index data as guide information are obtained from the CRT
display.
However, this system has problems in that the video tape must be
rewound to the tape top before searching and in that the number of
index data which can be indicated on one display is limited to
thereby make fine searching impossible.
The aforementioned searching systems have both merits and demerits.
If attention is given to the attempt to perform picture searching
by the signal processing of the VTR without complex operation
conducted by the operator, there is room for improvement in the
index system [3].
However, the index system has various disadvantages as described
above. The first disadvantage is that a special index marking means
such as a manual index marking means are required for using the
index signal effectively to make relatively fine searching
possible. The second disadvantage is that correlation between the
index and the picture existing at the position where the index is
marked is difficult, because the address of the index must be
designated by a numerical value in the searching operation. The
third disadvantage is that the middle position between index data
cannot be searched because pictures between the index data are
skipped when searching is executed. The fourth disadvantage is that
the system cannot answer some vague and sensory requirement, for
example, "where an interesting picture exists in the video tape"
caused by the fact that the index must be designated by a numerical
value and by the fact that the correlation between the index and
the picture cannot be grasped as an obvious image.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an
information recording/reproducing apparatus in which the index
system is employed as a precondition and in which a desired picture
can be searched at a high speed only by FF/REW operation with no
complex searching operation for designation of the address.
In order to attain the above object, according to an aspect of the
present invention, the rotary video head type information
recording/reproducing apparatus in which a video tape runs while
being in contact with a stationary head at the time of
fast-feeding/rewinding of the video tape, comprises: a read/write
memory for storing a picture signal for at least one scene; a
recording control circuit for digitizing at least one-scene picture
signal contained in a recording/reproducing picture signal at a
predetermined period so as to write the digitized one-scene picture
signal into the memory and for reading data of one-scene picture
signal written in the memory so as to record the data on the video
tape through the stationary head, in recording/reproducing
operation of the information recording/reproducing apparatus; and a
reproducing control circuit for reproducing data of one-scene
picture signal from the video tape through the stationary head and
for converting the reproduced data into analog data so as to output
the analog data.
The information recording/reproducing apparatus according to the
present invention operates in a manner as follows. In the
recording/reproducing operation mode of the information
recording/reproducing apparatus, the recording control circuit
digitizes at least one-scene picture signal contained in a
recording/reproducing picture signal at a predetermined period and
writes the digitized one-scene picture signal into the memory, and
then the recording control circuit reads out one-scene picture
signal from the memory and records on the video tape through the
stationary head. The recording position in the video tape is a
control track or an audio track with which the stationary head is
in contact. The above processing is executed at intervals of the
above-mentioned predetermined period with which each one-scene
picture is digitized.
Accordingly, picture signals for respective one-scene pictures
corresponding to index points at intervals of the above-mentioned
predetermined period are successively recorded in time series on
the video tape.
In order to perform picture searching in the FF/REW operation mode,
the reproducing control circuit reproduces the previously recorded
one-scene picture signal from the video tape through the stationary
head and converts the reproduced data into analog data so as to
output the analog data. Although the contents of the one-scene
picture signal outputted at this time change at intervals of the
above-mentioned predetermined period, the same one-scene picture
continues without changing for each interval of the above-mentioned
predetermined period and therefore the picture obtained on a
picture screen such as a CRT or the like is a still picture.
In summary, in picture recording/reproducing, a one-scene picture
is extracted at intervals of a predetermined period from a picture
signal and the extracted one-scene picture is recorded on a video
tape in synchronism with the picture signal, so that when it is
desired to perform picture search, a still picture which changes at
intervals of the predetermined period can be reproduced on a
picture screen of a display only by performing FF/REW operation.
Accordingly, an operator can perform search for a desired picture
at a high speed by referring to the timing of change of the still
picture actually displayed on the picture screen.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the present invention will be
apparent from the following description taken in connection with
the accompanying drawings, wherein:
FIG. 1 is a block diagram showing a first embodiment according to
the present invention;
FIG. 2 is a diagram for explaining the recording format according
to the present invention;
FIG. 3 is a diagram for explaining the CTL current waveform;
FIG. 4 is a diagram for explaining the construction of data in the
index code;
FIG. 5 is a diagram for explaining the construction of data in the
address code;
FIG. 6(a) is a diagram for explaining the form of original picture
display of the index video signal at the time of recording;
FIG 6(b) is a diagram for explaining the form of scale-down picture
display at the time of FF/REW;
FIG. 7 is a block diagram for explaining the operation at the time
of the REC-REC operation;
FIG. 8 is a block diagram for explaining the operation at the time
of the PLAY-REC operation;
FIG. 9 is a block diagram for explaining the operation at the time
of the FF/REW-PLAY operation;
FIG. 10 is a diagram for explaining the state of display at the
time of FF-PLAY; and
FIG. 11 is a diagram for explaining the state of display at the
time of REC-PLAY.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the accompanying drawings, preferred embodiments of
the present invention will be described hereunder.
To facilitate the understanding for readers, the contents of the
disclosure will be listed first.
FIRST EMBODIMENT
Preconditions
Common Constituent Parts between the Conventional VTR
and the First Embodiment of the Invention
Constitution of the First Embodiment of the Invention
Recording Format
Reduced-Scale Display
Operation
Circumstances in Practical Use
SECOND EMBODIMENT
Applied Example
First Embodiment
FIG. 1 shows a first embodiment of the present invention.
The preconditions will be now described hereunder.
This embodiment can be constituted by adding a signal processing
circuit 200 according to this invention to a conventional VTR 100,
on the preconditions that a video tape 2 runs while being in
contact with both a rotary head mechanism 5 and a stationary head 3
in the recording/reproducing mode of the conventional VTR 100 and
that the stationary head 3 is in contact with the video tape 2 in
the FF/REW mode. In brief, this reason why such preconditions are
required depends on the fact that the index scene for picture
searching is recorded in the control track or audio track of the
video tape 2 through the stationary head 3. The reason will be
apparent more in detail from the description which will be made
later.
When the aforementioned conditions are applied to the
recording/reproducing systems of real VTRs, .beta. type VTRs
satisfy the conditions. In the case of 8-mm video type VTRs, the
stationary head is not essential but the linear track of the tape
can be used. In the case of VHS type VTRs, a tape running mechanism
for performing fast feeding and rewinding in the state of the video
tape 2 of so-called "half loading" in which the stationary head 3
alone is in contact with the video tape 2 for the purpose of index
searching, is employed. Accordingly, the present invention can be
applied to the VHS type VTRs.
In the following, the construction of the embodiment according to
the present invention will be described.
In FIG. 1, the VTR is divided broadly into two constituent groups,
namely, the conventional VTR 100 and the signal processing circuit
200 according to the present invention.
The conventional VTR 100 has a VTR mechanism 1 for FF/REW running
of the video tape 2 in a "half loading" state, a stationary head
(hereinafter referred to as "CTL head") 3 being constantly in
contact with a control track of the video tape 2, a pinch roller 4
for feeding the video tape 2, the pinch roller being not in contact
with the video tape 2 at the time of the FF/REW, a rotary head
mechanism 5, a video signal input terminal 6, a video signal
recording/reproducing processing circuit 7, a video signal output
terminal 9, a servo system control portion 10 for the VTR mechanism
1, a CTL recording amplifier 13 for recording a CTL signal for
tracking, a connection cable 14 for connecting the CTL recording
amplifier 13 to the stationary head 3, a CTL reproducing amplifier
15, a group of control signals generated from the servo system
control portion 10, and other parts (not shown) such as an audio
recording/reproducing circuit, a tuner circuit, a timer reservation
circuit, and so on.
For the provision of the signal processing circuit 200, the
conventional VTR 100 is additionally provided with a video switch 8
for switching between a video signal 18 as an output signal of the
video signal recording/reproducing processing circuit 7 and a D/A
converter output signal 31 on the basis of the control of a
switching control signal 32, a CTL signal 12 subjected to necessary
modulation based on the recording CTL signal 11 from the servo
system control portion 10, the CTL signal 12 being fed to the CTL
recording amplifier 13, and a reproducing CTL signal 16 being fed
to a demodulator portion 27.
The signal processing circuit 200 is constituted by an RAM (having
a capacity for one frame/field) 22 serving as a memory capable of
reading/writing a one-scene video signal (hereinafter referred to
as "index video signal V.sub.IDX " for discrimination from the
video signal 18) suitably selected from the video signal 18, a
recording control circuit 300 for performing control on the
recording of the index video signal V.sub.IDX, and a reproducing
control circuit 400 for performing control on the reproducing of
the index video signal V.sub.IDX at the time of searching.
The recording control circuit 300 is constituted by an A/D
converter portion 19 for converting the video signal 18 as an
output signal of the video signal recording/reproducing processing
circuit 7 into a digital signal, a synchronizing separation circuit
20 for separating horizontal and vertical synchronizing signals
from the video signal 18, a writing control circuit 21 for
controlling the A/D converter portion 19 on the basis of the
synchronizing signals to thereby determine the address of the
digital data, a data bus line, an encoder portion 25 for encoding
picture data stored on the RAM 22 according to a predetermined
format, and a modulator portion 26 for modulating the CTL recording
signal based on the encoded data The recording format of the index
video signal V.sub.IDX to the video tape 2 by the encoder portion
25 will be described later.
The reproducing control circuit 400 is constituted by a demodulator
circuit 27 for demodulating data from the reproducing CTL signal
16, a decoder portion 28 for reconstructing picture data from the
demodulated data and for correcting or compensating the picture
data, a reading control portion 29 for performing RAM control and
video switch control for the purpose of display based on the
synchronizing signals, a D/A converter portion 30 for converting
the picture data into an analog video signal, a D/A converter
output signal 31 as an output signal (that is, reproducing index
video signal) of the D/A converter portion 30, and a switching
control signal 32 for switching over the video switch 8 to send the
D/A converter output signal to a video signal output terminal 9.
The form of display (reduced-scale display) of the D/A converter
output signal 31 fed from the video signal output terminal 9 to a
CRT screen not shown will be described later.
In the aforementioned configuration, the block diagram shown in
FIG. 1 expresses the connection of a signal processing. In
practice, the aforementioned constituent parts can be controlled by
a micro-processor (micro-computer). The total operation control on
the encoder portion 28, the modulator portion 26, the demodulator
portion 27 and other signal processing portions not shown can be
constituted without discrete logic processing and analog
processing.
Although this embodiment has shown the case where the CTL signal is
used among recording signals in use of the stationary head 3, the
present invention is applicable to the case where an audio track or
the like may be used.
In the following, "recording format" is described.
In the case where a picture is recorded after being digitized, the
following items are important for the formats (in which still
picture display will be described).
(1) Quantizing Method: picture element constitution and bit number
per picture element.
(2) Encoding Method: interleave, error detection/correction code,
compensating system, high-efficient encoding.
(3) Modulating Method: transmission rate, error rate, band
compression.
In this embodiment, preconditions for determining these formats are
decided as follows.
(a) Index video signal V.sub.IDX data are recorded on a control
track. Therefore, no influence on tracking as an original object of
CTL is required. Further, no mistake for index/address information
is required.
(b) The recording of one scene of the index video signal V.sub.IDX
must be finished just in five minutes. Assuming that FF/REW is at a
50-fold speed, the updating period is 6 seconds. In the case where
a recording is made in a 3-fold mode, the updating period is 2
seconds because the speed of FF/REW corresponds to a 150-fold
speed.
(1) Quantizing Method
From the precondition (b), all one-scene index video signal
V.sub.IDX data and additional data must be recorded in 5
minutes.times.60 seconds.times.30 frames per second=9000
frames.
As well known, one wave of the CTL signal is recorded in one frame.
Assuming that data is added in the form of modulation of the duty
ratio of the CTL signal, one-scene index video signal V.sub.IDX
data must be in the range of 9000 bits. Further, additional data
other than the picture data, such as synchronizing bit for
expressing a data block, address for the address of the data block,
error detection code, and the like, must be contained in the
recording data. Therefore, picture data are established to be about
8000 bits. Assuming that one picture element is composed of 4 bits
(16 tone steps, monochrome), 2000 picture elements can be provided.
In this embodiment, 44 (picture elements per line).times.45
(lines)=1980 picture elements are provided.
4 bits .times.1980=7920 bits
The RAM 22 in FIG. 1 may be constituted by a 2 kw.times.4 bits
memory element.
(2) Encoding Method
It is general that the total transmission bit number=9000 is
divided into blocks having a suitable length and that additional
data, such as block synchronizing signal, block address, error
detection/correction code, and the like, are added to each block.
In this embodiment, 45 blocks per line are provided. Accordingly,
the bit number of one block is represented by the equation: 9000
bits.div.45=200 bits per block.
Of the 200 bits, the bit number of the picture data is represented
by the equation: 44.times.4=176 bits. The bits which can be added
are 24. When block address is added to each block, 6 bits are
required. If 2 bits of the residual 18 bits are used for block
synchronization, 16 bits can be used for error
detection/correction. The recording data thus formed in order are
shown in FIG. 2.
Two bits of synchronizing data are placed in the lead of the block
and are discriminated from other data by changing the modulating
system. Six bits of address data are binary-coded and the value
thereof increases by one for each block to take the range of from 0
to 44 (45 lines). Each picture element data is composed of 4 bits,
so that 44 picture elements of the line designated by the block
address are given in order. Sixteen bits of error-detecting or
correcting code such as CRC produced by a predetermined formula are
given lastly so that the total number becomes 200.
In this embodiment, encoding techniques are described, inclusive of
quantizing techniques but exclusive of high-efficient
techniques.
(3) Modulating Method
For example, in a VHS-type VTR, it is not preferable that an audio
signal recording system through the stationary head is used for
other purposes, because no frequency-modulated Hi-Fi audio signal
may be recorded. Therefore, in this embodiment, multiple modulation
is made on the CTL signal 12.
As well known, the leading edge (the point in which the remanence
on the tape is changed from S to N) of the CTL recording current as
shown in FIG. 3 is necessary for reproducing tracking which is an
original object of the CTL signal 12. On the other hand, the
position of the trailing edge (the point in which the remanence on
the tape is changed from N to S) is not limited. In other words,
duty ratio (=tN/tF) is not limited.
As described preliminarily in the prior art, searching by
superposing index or address information on the CTL signal 12 has
been used in practice in recent years. As well known, the duty
ratio may be divided into two ranges to express two digital data
"1" and "0".
Data "0".fwdarw.duty ratio 60.sup..+-.5 %
Data "1".fwdarw.duty ratio 27.5.sup..+-.2.5 %
The index code and the address code are effectuated in combinations
of data "0" and "1" as shown in FIGS. 4 and 5. Accordingly, there
is no mistake if data are out of the two duty ratio range. Further,
there is no mistake if eight or less CTL signals having the duty
ratio corresponding to the data "1" are continuous.
For this reason, duty ratios in modulation in this embodiment are
established as follows.
Data "0".fwdarw.duty ratio 55%
Data "1".fwdarw.duty ratio 75%
Sync "0".fwdarw.duty ratio 75%
Sync "1".fwdarw.duty ratio 27.5%
Although 27.5% duty ratio corresponding to the aforementioned index
data "1" is also used in synchronizing in this invention, there is
no mistake because the synchronizing data is only one for 200
frames.
In the following, reduced-scale display is described.
In this embodiment, the number of picture elements per one scene is
established to be low, because nothing but very low transmission
rate of 1 bit per 1 frame (that is, 30 b/s) can be obtained for the
reason that superposing is made on the CTL signal.
(44.times.45=1980 picture elements)
In the case where a still picture consisting of 1980 picture
elements is inserted in the video signal 18 at the time of FF/REW,
a display area having size vertically and horizontally reduced to
about 1/5 of the TV screen can be obtained by assigning 45 lines of
the still picture to 45 lines (vertical direction) of the video
signal 18 and assigning one line (44 picture elements) of the still
picture to about 10 .mu.s of the horizontal synchronizing signal of
the video signal 18. The reduction rate of the practical picture
size is set to be less than the reduction rate of the display size.
In short, the reduction rate of the practical picture size is set
to be 1/4 of the TV screen size. The original picture at the time
of recording is cut out so that the center portion of the original
picture is quantized. Accordingly, the contents of the still
picture is made easy to see though the display size is small.
In respect to the horizontal direction, 44 picture elements are
sampled in a period of 0.91 .mu.s (1.1 MHz). This sampling
frequency (1.1 MHz) is 70 times as high as the horizontal scanning
frequency f.sub.H. The center portion of the picture signal of
0.91.times.44=40 .mu.s is sampled from the picture signal of about
52 .mu.s in the horizontal direction. When the sampled signal is
displayed at the time of FF/REW, D/A conversion is made in the
frequency of 4.4 MHz (280.times.f.sub.H) which is four times as
high as the ordinary sampling frequency. In short, reduced-scale
display is made in a period of 10 .mu.s in the horizontal
direction.
In respect to the vertical direction, one line is sampled in a
period of 4 lines. Although about 220 effective scanning lines
exist in the vertical direction, one line is sampled for every
three lines on the center portion thereof having 4.times.45=180
lines. In the case where the signal is displayed at the time of
FF/REW, the sampled signal is sent to each H (45 lines) with a
suitable line of the video signal 18 output picture as a starting
line. Accordingly, at the time of display, the original picture of
180 lines is scaled down to the scale of 45 lines which is 1/4 as
much as the original scale of 180 lines. Consequently, an original
picture shown in FIG. 6(a) is scaled down to a reduced-scale
picture shown in FIG. 6(b).
The reduced-scale display is a known system called "picture-
in-picture". In the display according to the present invention, the
reduced-scale screen is constituted by one-field still picture.
Accordingly, the same reduced-scale still picture can be inserted
in each field without discrimination between even and uneven fields
of the video signal 18 picture.
First, the operation (hereinafter referred to as "REC-REC") of
recording the index video signal V.sub.IDX in the recording mode of
the VTR is described.
Here, the outline of the operation is described to assist the
understanding of the readers. The outline of the flow of main
signals at the time of the "REC-REC" operation is shown in FIG. 7.
As shown in FIG. 7, the video signal received from the video signal
input terminal 6 is sent as a through output from the video signal
recording/reproducing processing circuit 7 to the video switch 8
and then branched as a video signal 18 to the A/D converter portion
19. Data of the video signal 18 digitally coded by the A/D
converter portion 19 are once stored in the RAM 22 through the data
bus line 23. Then, the data of the video signal 18 are read from
the RAM 22 and encoded in a predetermined format by the encoder
portion 25 through the data bus line 23. The encoded data are
modulated by the modulator portion 26. After the modulated data is
superposed on the CTL signal 12, the data are passed through the
CTL recording amplifier 13 and the connection cable 14 and recorded
on the control track of the video tape 2 through the stationary
head 3.
In the following, the "REC-REC" operation is described more in
detail.
The consideration that the recording of the conventional index
address information is not impeded is required for recording the
index video signal V.sub.IDX. Therefore, the control portion
generalizing the signal processing portion not shown after
receiving the fact that the VTR portion is in the recording mode
(hereinafter referred to as "REC") judges whether index information
(duty ratio=27.5%) is superposed on the recording CTL signal from
the VTR portion or not. Index information is generally designed to
be automatically given to the starting point of the REC, so that,
in most cases, the judgment becomes valid. The judgment is made in
the encoder portion 25. If 27.5% duty ratio is produced even in one
frame, the recording CTL signal 11 is sent as a CTL signal 12 with
no change of the duty ratio. The recording CTL, signal is held
longer (93 frames or more) than the time required for the index and
address codes. If 27.5% duty ratio is given during the superposing
of the picture data which will be described later, the picture data
superposing process is interrupted for the period of 93 frames to
send the recording CTL signal 11 as a through output to the CTL
signal 12. Accordingly, there is no bad influence on the recording
of the index and address information of the conventional VTR.
In the case where the recording CTL signal 11 input is out of the
index and address codes, the output video signal 18 of the video
signal recording/reproducing processing circuit 7 is digitally
converted after the frequency is limited to the band which is about
half as high as the AD conversion clock frequency. The digital data
thus obtained are passed through the digital data bus line and then
stored in the RAM. The AD conversion data from the A/D converter
portion 19 are stored in the RAM 22 by 44 samples per one line for
every three lines on the basis of the synchronizing signal
separated by the synchronizing separation circuit 20. This is
perfected if one-field data are stored. The writing control circuit
21 serves to control this operation. The circuit 21 starts the
counting of signal pulses from the vertical synchronizing signal of
the field to be stored, for example, counts signal pulses in
70.times.f.sub.H from the horizontal synchronizing signal of the
46th line till data in 44 clock pulses from the 18th clock to the
63th clock are stored in the RAM 22. The addresses in the RAM are 0
to 43. Next, 44 picture elements in the 50th line are sampled in
the same manner as described above, so that data are respectively
stored in the addresses 44 to 87 of the RAM. When this operation is
lastly made about the 222nd line, the storage of one-scene data of
45 lines is perfected. The RAM address of the last data is 1979.
Data of 4 bits forming one picture element are stored in each RAM
address. In short, data processing on the are a surrounded by the
dot-and-dash line in FIG. 6(a) is finished
After the data storage into the RAM 22 is perfected, data
modulation on the CTL signal is started frame by frame. Because
9000 frames (5 minutes) are required for sending out one-scene
data, the storage of the next scene into the RAM 22 is conducted in
any field of the last frame in which data are sent out.
In the following, the encoder portion 25 and the modulator portion
26 for forming data stored in the RAM 22 according to the recording
format are described.
The both portions operate with the leading edge of the recording
CTL signal as reference timing. As described above, 3 duties (that
is, falling timing) are given to the modulator portion 26 based on
4 kinds of data (data "0", "1", synchronizing signal "0", "1") from
the encoder portion 25 and form as a CTL signal 12 output. Because
one frame corresponds to about 33.37 ms, the leading edge of the
recording CTL signal 11 makes the CTL signal rise up soon. Then,
the CTL signal 12 is made to fall down by data from the encoder
portion 25 after 18.4 ms in the case of data "0", after 25.0 ms in
the case of data "1" or synchronizing signal "0" and after 9.2 ms
in the case of synchronizing signal "1", respectively.
The encoder portion 25 feeds data (containing synchronizing data)
one by one for each frame according to the order of the data as
shown in FIG. 2.
After synchronizing signal "1", synchronizing signal "0" and
address data of 6 bits (in which all bit data are "0" because the
line address value is 0) are sent out for each frame after one
scene is stored as described above, the encoder portion 25 makes
reading access to the RAM 22 to fetch data of the RAM address 0.
The fetched 4 bits are sent out in order. When the sending-out of
the 4 bits is finished, the encoder portion 25 makes access to the
RAM address to send out 4 bits one by one in order. After the
aforementioned operation repeated till 4 bits in the RAM address 43
is sent out, 16 bits of error detection/correction code (for
example, CRC code) are sent out as the next frame. The block as
described above is a block of the line address 0. In the next
frame, synchronizing signal "1" of the next block (address value 1)
is sent out. Similarly, synchronizing signal "0", address data of 6
bits (in which the LSB is "1" and other bits are all "0"), 4 bit
data of the RAM address 44, . . . are successively sent out. When
16 bits of CRC are sent out after 4 bits of the RAM address 87 are
sent out, the block of the line address 1 is perfected. The
aforementioned operation is repeated till the block of the line
address 44 is sent out. Thus, 9000 bits corresponding to one scene
is recorded.
If the storage of the next scene into the RAM 22 is made
simultaneously in one field of the last frame in the block of the
line address 44, the next one-scene data can be recorded by
returning the operation to the start of the aforementioned
paragraph. The operation of fetching video signal as a still
picture during recording at intervals of a predetermined period (5
minutes) and superposing the signal as digital data on the CTL
signal for the predetermined period (5 minutes) is repeated.
During the sending of bit data, an error-detecting/correcting code
is calculated by suitable producing means from the total 182 bits
of address data 6 bits and picture element data 44.times.4 bits
contained in one block, so that the thus obtained code is sent out
lastly in the block. In this embodiment, 16 bits of CRC (cyclic
redundancy check) code are used for the single purpose of error
detection. For example, the following producing polynomial
recommended by CCITT can be used.
In the following, the operation of recording (hereinafter referred
to as "PLAY-REC") of the index video signal V.sub.IDX in the
reproducing mode of the VTR is described.
The outline of the operation is now described. The outline of the
flow of main signals at the time of the "PLAY-REC" operation is
shown in FIG. 8. As shown in FIG. 8, the video signal reproduced
from the video tape 2 by the rotary head mechanism 5 is sent out to
the video switch 8 through the video signal recording/reproducing
processing circuit 7 and is branched. Then, the signal is digitally
coded as a video signal 18 by the A/D converter portion 19. The
data of the video signal 18 are once stored in the RAM 22 through
the data bus line 23. Then, the data of the video signal is read
from the RAM 22, converted in a predetermined format by the encoder
portion 25 through the data bus line 23, superposed on the CTL
signal 12 after modulation in the modulator portion 26, passed
through the CTL recording amplifier 13 and the connection cable 14
and recorded on the control track of the video tape 2 through the
stationary head 3.
In the following, the "PLAY-REC" operation is described more in
detail.
The "PLAY-REC" operation can be established on condition that a
certain video signal has been recorded on the video tape but no
picture data is superposed on the control track. If after-recording
of the index video signal V.sub.IDX is made on the video tape 2,
the function of this embodiment for displaying the index video
signal V.sub.IDX at the time of FF/REW can be added.
In the ordinary reproducing mode PB of the VTR, the video signal 18
of the video signal recording/reproducing processing circuit 7 in
FIG. 1 is a reproducing video signal from the video tape 2. The
picture data to be recorded is stored in the RAM 22 after the video
signal 18 is subjected to A/D conversion by the A/D converter
portion 19. Then, a necessary data train is formed from the video
signal by the encoder portion 25. Then, a necessary duty ratio is
given corresponding to the data by the modulator portion 26 in the
same manner as in the "REC-REC" mode.
In the case of the ordinary reproducing mode PB of the VTR, the
leading edge of the CTL signal 12 must be at least reproduced at
the first step for the purpose of tracking. The timing thereof must
accord with the recording CTL signal 11 which is a timing reference
signal for the encoder portion 25 and the modulator portion 26.
Accordingly, it is necessary to lead in the ordinary reproducing
tracking servo previously to the recording of the index video
signal V.sub.IDX, confirm the stability thereof and perform the
switching in the recording/reproducing frame of the CTL signal 12
that the CTL reproducing amplifier 15 and the CTL recording
amplifier 13 are made active and inactive, respectively, in a
period before and after the rising pulse of the reproducing signal
and that the activities of the amplifiers are reversed in other
periods. The switching signal (not shown) for the switching can be
generated by the servo system control portion 10 or modulator
portion 26. Of course, this is a consideration necessary in the
case where the recording and reproducing of the CTL signal 12 are
constituted by using one head commonly (as in almost VTRs). If the
stationary head 3 is configured so as to provide recording and
reproducing separately (or provide after-recording separately) or
if the index video signal V.sub.IDX is recorded on another
independent track without multiple modulation of the index video
signal on the CTL signal in the control track, the aforementioned
consideration is unnecessary.
In the case of the ordinary reproducing mode PB of the VTR, there
are two points to be considered further. The first point is in the
case where the leading edge in the reproducing CTL signal 16
becomes absent in the reproducing period during the recording of
the index video signal V.sub.IDX after the reproducing period of
the CTL signal 12 is determined. In this case, the recording of the
CTL signal 12 is interrupted to perform re-tracking with the CTL
signal 12 changed to continuous reproducing. The second point is in
the case where the recording mode (recording time, for example,
standard or three-fold) of the video signal on the video tape 2 is
changed. Although disorder at the switching point can be eliminated
by the consideration for the first point, CTL signal 12 pulses of
three waves are reproduced in one frame at the switching point from
the standard mode to the three-fold mode. If the phase of one wave
of the three waves accords with the phase of the CTL signal 12
pulse in the standard recording portion, the signal cannot be
detected. Accordingly, the problem can be solved by performing the
reproduction of the CTL signal 12 in the period of one frame at
suitable intervals (for example, 1 block=6.7 seconds) during the
standard mode reproduction and confirming that one reproducing CTL
signal 16 exists.
In the following the operation of reproducing (hereinafter referred
to as "FF/REW-PLAY") of the index video signal V.sub.IDX in the
FF/REW mode of the VTR is described.
The outline of the operation is now described in the same manner as
in the description for the aforementioned modes. The outline of the
flow of main signals at the time of the "FF/REW-PLAY" operation is
shown in FIG. 9. As shown in FIG. 9, the index video signal
V.sub.IDX recorded on the control track of the video tape 2 is
reproduced through the stationary head 3, passed through the
connection cable 14 and the CTL reproducing amplifier 15, fed as a
reproducing CTL signal 16 to the demodulator portion 27 and decoded
through the decoder portion 28. Then, the decoded signal is stored
in the RAM 22 again through the data bus line 23. On the other
hand, the signal is read from the RAM and fed to the D/A converter
portion 30 through the data bus line 23. After D/A conversion in
the D/A converter portion 30, the signal is fed as a D/A converter
output signal 31 to the video switch 8 so that the signal is given
the to TV receiver set from the video signal output terminal 9. At
this time, the contents of the index video signal V.sub.IDX are
displayed in the form of a still picture on the TV screen. The
detailed aspect of the display will be described later.
In the following, the "FF/REW-PLAY" operation is described more in
detail.
In the case where the VTR mechanism 1 is in a mode in which the
video tape 2 runs at a high speed and in a state in which no signal
but video signal having deviated synchronizing signal frequency to
make normal synchronization impossible in the TV receiver set can
be obtained or in a state in which no video signal can be
reproduced, that is, in the case of the FF/REW mode, the tape speed
generally varies widely. This reason is that high-speed feeding is
attained by driving a reel mount without driving the video tape 2
through the pinch roller 4 as in the ordinary recording/reproducing
mode and, on the contrary, the winding diameter of the video tape 2
changes with the taking-up thereof to bring about the change of the
tape speed. Accordingly, the period of the reproducing CTL signal
16 to be reproduced also changes.
Further, in general, the tape speed in the FF/REW mode in the case
where the tape has been recorded in the standard mode is not
different from the tape speed in the FF/REW mode in the case where
the tape has been recorded in the three-fold mode. Accordingly, the
period of the reproducing CTL signal 16 is different by three
times. When the change of the winding diameter of the tape is added
to this, the change of the period becomes more excessive.
Therefore, a proposal of controlling the tape speed based on the
rotational speed of the two reel mounts or the frequency of the
reproducing CTL signal 16 to stabilize the tape speed to some
degree has been made. However, the change of the period of the
reproducing CTL signal 16 must be considered to about 1/200 as much
as the one-frame period in the case of normal reproduction.
In FIG. 9, the reproducing CTL signal is amplified by the CTL
reproducing amplifier 15 and then the output reproducing CTL signal
16 thereof is converted into square wave as the waveform (FIG. 2)
of the recording CTL signal 11. As well known, the output of the
stationary head 3 is produced in the form of so-called differential
pulse of polarity according to the direction of inversion at the
polarity inverting point of magnetization. Accordingly, the CTL
reproducing amplifier 15 is constituted to have integral
characteristic or to contain a flip-flop circuit (bistable trigger
circuit) to be set/reset based on the polar pulse.
The demodulator portion 27 operates as follows. Data are settled
corresponding to the duty ratio based on the reproducing CTL signal
16 in which the period changes widely. Accordingly, it is
preferable to perform duty ratio measurement independently for each
wave of the reproducing CTL signal 16. Therefore, the time t.sub.N
from the leading edge of the reproducing CTL signal 16 having
waveform as shown in FIG. 2 to the trailing edge thereof is
measured. Then, the time t.sub.S from the falling to the rising is
measured. During the measurement of the next t.sub.N, the value of
d is calculated from the measured values t.sub.N and t.sub.S by the
equation:
in which d represents the value obtained by subtracting 1 (one)
from the reciprocal of the duty ratio used in the description of
modulation. Of course, the duty ratio may be calculated as
follows.
This is for simplification of calculation. The value related to the
found duty ratio is compared with a predetermined judgment value,
so that data (containing sync) are decided. As described above, the
measurement of the time between the edges of the CTL signal 12 and
the calculation/data-detection are made simultaneously. The decided
data are transmitted to the decoder portion 28, successively. Above
description is in the case where the tape running is in the forward
direction (that is, FF).
When the tape running is reverse (that is, REW), the signal
sequence is reversed. Accordingly, t.sub.S is measured first. When
the next t.sub.N is measured, d is calculated as follows.
The decoder portion 28 operates as follows. The flow of the
processing is, successively, (1) detection of block synchronizing
signal, (2) storage of address and picture element data into the
buffer memory, (3) error detection, (4) correction/compensation and
(5) transfer to the display memory.
(1) Detection of Block Synchronizing Signal
The block synchronizing signal can be detected by checking the bit
series of synchronizing "1" data and synchronizing "0" data from
the demodulator portion 27. In this format, one "1" data exists in
the block synchronizing portion and the other, 199 bits take the
value of "0" ("1" or "0" in picture element data). If continuous
synchronizing "1" data of 2 bits or more do not exist, the
synchronizing "1" data can be considered to be not conventional
index or address code, but block synchronizing.
(2) Storage of Address and Picture Element Data into Buffer
Memory
When the block synchronizing signal is detected, the addresses (0
to 199) in the block of the following data can be decided.
Accordingly, the data train is separated into the block addresses,
44 picture element data in the block, and CRC data. The addresses
and the picture element data are stored in predetermined positions
of the buffer memory.
(3) Error Detection
A cyclic arithmetic operation according to a predetermined
producing formula is performed on the addresses, the picture
element data and the CRC data. If there is no error, the block is
considered to be valid. If there is any error, the block is
considered to be invalid.
(4) Correction/Compensation
If error bit can be specified on the error-detected block by an
error detecting system, the error bit is corrected. If error
correction is impossible, a compensating operation, for example, an
operation of sending out again data in a block (line) just prior to
the block, is performed.
(5) Transfer to Display Memory
The picture element data subjected to the aforementioned processing
(4) are transferred to the RAM 22 through designation of the RAM
addresses determined by the line number and the picture element
number in the line. As a result, the displayed picture is updated
successively.
Above description is applied to the case where the running
direction of the video tape 2 is the forward direction (FF). In the
reverse direction (REW), however, the data train is reversed.
Accordingly, the address 199 in the block is given to the data next
to the block synchronizing. Thereafter, the address number is
decreased one by one. If writing in the buffer memory is designated
based on the address in the block, new data enter in the reverse
direction. In respect to the CRC calculation, the same arithmetic
operation as in the case of the FF direction may be performed
simultaneously because the block contains the same data as in the
case of the FF direction. Alternatively, the arithmetic operation
circuit (or software) may be replaced to perform a reversed-trace
arithmetic operation for each bit of the reverse-direction data. It
is a matter of course that the direction of correction is
reversed.
The processing in the decoder portion 28 has been described in
brief. In short, the procedure of successively encoding data stored
in the RAM 22 at the time of recording to convert the data into a
recording data train is performed reversely and, further, error
correction/compensation is performed. Although the compensation in
this description is made by substituting the just prior line for
the error line, the buffer memory having the capacity for one line
(block) is sufficient for such simple compensation. If no
compensation is made, the buffer memory becomes unnecessary. If the
interleaving of data (picture elements) is used in the recording
format, fine compensation is made possible and, at the same time,
introduction of error correction is made easy. In this case, the
buffer memory requires the capacity corresponding to the
interleaving distance.
These conditions are to be determined generally on consideration of
factors, such as bit error rate from the step of modulation to the
step of demodulation, statistical characteristic (random
characteristic, burst characteristic) thereof, display picture
quality and residual error tolerance, realization of the processing
means, and the like.
In the following, the displaying operation by means of the reading
control portion 29 is described.
The picture data reconstructed by the aforementioned decoding
process have been transferred into the RAM 22. The object of the
reading control portion 29 is to insert the contents of the
reconstructed picture data as a reduced-scale display into the
video output of the VTR. Although the outline of the reduced-scale
display has been described above, the reduced-scale display will be
described more in detail with reference to FIGS. 6(a) and 6(b).
The area surrounded by the one-dotted chain line is a subject of
scale reduction on the original picture as shown in FIG. 6(a)
because of the limitation of the number of the picture elements.
The data which have been reproduced through the decoder portion 28
and other portions are transferred into the addresses of the same
RAM 22 as in the storage state of the index video signal V.sub.IDX
at the time of recording. For the purpose of performing scale-down
display of the data stored in the RAM 22 as shown in FIG. 6(b), it
is necessary to count up the value (0 to 1979) of the counter for
generating the read-out address of the RAM to thereby make the
count value of the counter accord with the display area and
increase the clock frequency to the scale-down rate (4 in this
embodiment).
The reading control portion 29 further has a delay circuit for
giving a time (line number in the V direction ) from the
synchronizing signal to the starting of scale-down display both in
the horizontal (H) direction and in the vertical (V) direction, and
a display period counter for generating signals for expressing the
display period of 44 clock pulses (10 .mu.s) in the H direction and
the display period of 45 lines in the V direction. The conjunction
or logical product of the two display period signals in the H and V
directions forms a display area signal, that is, a switching
control signal 32. If the time to the starting of the display in
the delay circuit is changed, the position of the scale-down
display portion in the video signal in FIG. 6(b) can be changed
suitably.
The counter for generating the read-out address of the RAM 22 is
designed to be reset at the starting point of the display area and
to be counted in the period in which the display area signal is
active. The counter takes the value from 0 to 43 in the first line
display period (10 .mu.s). In the next line, the value of the
counter is counted up from 44 to 87. In the last line, the value of
the counter is started from 1936 so that the display of one still
picture is perfected in the last picture element of 1979. The
aforementioned displaying operation is repeated in each field of
the video signal 18 of the video signal recording/reproducing
processing circuit 7.
Further, the reading control portion 29 may generate a picture
frame signal related to the generation of the display area signal
to thereby add a frame to the peripheral of the scale-down display
screen in FIG. 6(b). For example, the picture frame signal is
constituted by an extension portion formed by extending the display
area by two lines both in the upward direction and in the downward
direction and by two picture elements both in the left and in the
right. The picture frame signal may be constituted so that the
video level (arbitrary level from black to white of the frame
portion applied to the switching position added to the vide switch
8 can be selected based on the picture frame signal to be led to
the video signal output terminal 9. Alternatively, the picture
frame signal may be constituted so that the output of the D/A
converter portion 30 gives the level of the frame based on the
picture frame signal and that the ORing of the picture frame signal
and the switching control signal 32 is made.
The D/A converter portion 30 serves to convert digital data into
analog voltages to shape up the signal capable of being switched
and inserted into the video output signal through the suitable
limitation of the band. The output signal is the D/A converter
output signal 31.
In the following, the switching control circuit 32 is described
supplementarily.
Description about the writing of data into the RAM 22 and the
reading of data from the RAM 22 has been made. In the case where
access to the RAM 22 is made through the data bus line in the block
construction as shown in FIG. 1, attention must be paid to
competition for access, in particular, between the writing of the
index video signal and the reading of still-picture data from the
RAM 22 as a display memory.
There arises no problem in the recording mode. Of the 9000 frames,
the number of frames capable of being subjected to reading access
from the RAM (frame / field) 22 is 44.times.45=1980 frames (once
per frame). Accordingly, of the 9000 frames, the room of 1 field
for performing writing access into the RAM exists.
In the reproducing mode and FF/REW, in respect to the display area,
the RAM data must be read and transferred to the D/A converter
portion 30. On the contrary, the writing transfer for transferring
reproduction-decoded data into the RAM 22 must be considered to
occur randomly because of the change of the tape speed. In short,
there is a possibility that a request for writing data in the RAM
22 may be issued while data is read from the RAM 22 during the
display.
As a countermeasure, the clock period (1.1 MHz.fwdarw.0.9 .mu.s)
during the display may be divided to make it possible to perform
both the writing in the RAM 22 and the reading from the RAM 22
substantially in parallel. Alternatively, as another
countermeasure, the period of 10 .mu.s of reading access from the
RAM 22 may be defined as a writing-disabled period in which the
transfer of data from the decoder portion 28 to the RAM 22 is
deferred temporarily.
Memory chips used as the RAM 22 can be determined generally by
factors, such as easiness of picture element construction control,
and cost, inclusive of the aforementioned processing methods. In
this embodiment, the highest speed is required for the reading
period for displaying. However, the reading period is no more than
0.9 .mu.s. Accordingly, a general purpose dynamic RAM can be used
though refreshing control is required. In the point that control is
simple and easy to handle, an SRAM (static RAM) may be used.
In the following, the states of the respective parts are described
in the case where the VTR of this embodiment is used
practically.
If there is no index video signal V.sub.IDX superposed on the CTL
signal 12 and recorded in advance, it is a matter of course that
the object of the present invention cannot be attained. The
multiple recording of data is constructed so that still-picture
data are automatically superposed by the running of the tape based
on the following operations of the VTR:
(i) During execution of recording based on reservation or manual
operation;
(ii) The case where the fact that index video signal V.sub.IDX data
are not multiplexed is judged in reproducing operation; and
(iii) The case where a mode (a kind of reproducing mode) for
after-recording index video signal V.sub.IDX is operated.
Paragraphs (ii) and (iii) show methods for after-recording data on
a video cassette on which data containing no index video signal
V.sub.IDX has recorded by a conventional recording method. If the
index video signal V.sub.IDX is recorded on the cassette, the index
signal which has been recorded is destroyed. Accordingly, it is
preferable that an operating portion for performing after-recording
is provided as shown in paragraph (iii). In the mode of paragraph
(iii), after-recording can be made easily in the period of no use
of the VTR by providing automatic mechanisms, such as a mechanism
for prohibiting the reception of other operations, a mechanism for
returning the tape to the top thereof and then starting
after-recording, a mechanism for automatically rewinding the tape
and cutting off the electric source of the VTR when executing the
running of the tape to the end thereof, or the like.
Although description has shown that the storage of the index video
signal V.sub.IDX into the RAM 22 is executed just after the mode of
the VTR is turned to the recording mode or after the execution is
deferred for the period of several seconds in which the
conventional index signal may be recorded, and the data are slowly
superposed on the CTL signal 12 for the period of 9000 frames (5
minutes) so that the next index video signal V.sub.IDX is stored
repeatedly when the superposing of the index video signal is
finished, the index video signal may be restored in the following
cases to re-start the recording of 9000 frames eve in the middle of
the data recording of 9000 frames:
(i) The case where the recording or reproducing mode is once
canceled and then set again;
(ii) The case where pause (waiting) is given in the recording mode
and then recording is re-started;
(iii) The case where index or address information is recorded;
and
(iv) The case where an instruction is given to restore a still
picture by manual operation.
Reproduction of Still Picture Data . . . FF/REW
In general, the VTR is constituted so that the input video signal
is led to the output terminal in the period other than that time of
the ordinary reproducing mode PB. In the ordinary reproducing mode
PB, it is a matter of course that the reproducing video signal is
sent out. The term "input video signal" means a signal selected
from the line input from the outside and the video signal received
by the built-in TV tuner FIG. 6(b) shows the condition that a
reproducing still picture is inserted into the selected video
signal. As described above in the operation in FIG. 1, a
synchronizing signal must exist in the output video signal 18 of
the video signal recording/reproducing processing circuit 7 for the
purpose of inserting the still picture. Accordingly, the video
signal recording/reproducing processing circuit 7 has a function
for generating a synchronizing signal (which may contain suitable
video signal . . . for example, blue) instead of the input video
when the input video does not exist.
Assuming that the FF or REW operation is given to the VTR, when the
picture on the basis of the video signal from the output terminal 9
is watched on the TV screen, the scale-down display area as shown
in FIG. 6(b) appears in some display. The picture in the scale-down
display area is blank in the initial stage. When the running of the
video tape is started, the decoding process and the transfer of the
display data into the RAM 22 as described above are executed
corresponding to the running of the tape, so that the picture in
the display area is gradually perfected. The term "gradually" means
the fact that data (contents of the picture) enter from left to
right in a certain line of the 45 lines in the case of the FF
operation so that a data next to the right end of the line enters
into the left end of a line under the line. A line next to the
lowermost line enter as the uppermost line of the next still
picture so that data are updated downward. In the case of the REW
operation, the reproducing data (picture element) train is reverse.
Accordingly, updated data enter from left of a line to right so
that a data next to the left end of the line enter into the right
end of a line above the line. A line next to the uppermost line
enter as the lowermost line of the just prior still picture (with
respect to the time axis at the time of recording) so that data ar
updated upward.
In this embodiment, the updating rate is one picture per five
minutes. Assuming now the FF/REW speed is 50 times as high as the
recording speed, the updating of one picture (45 lines) is made in
the period of 0.1 minutes=6 seconds. In the portion recorded in the
three-fold mode, one picture is updated in the period of 2
seconds.
Consequently, because display as described above is made according
to this embodiment, still picture data are updated downward as
shown in FIG. 10 at the time of the FF operation and, on the
contrary, still picture data are updated upward as shown FIG. 11 at
the time of the REW operation. Accordingly, so-called vertical wipe
switching can be attained, so that the direction of the running of
the tape can be found. Because the real time required for drawing
one still picture is a value of 5 minutes with no fraction, the
quantity of the running of the tape can be found in an analog sense
from the number of updated still pictures and the updated position
of one still picture at the time of the FF/REW operation. A
function that "the contents of the tape running at the time of the
FF/REW operation can be known in the form of a picture by the same
operation as in the conventional VTR as a first object of the
present invention can be attained.
Second Embodiment
The aforementioned first embodiment is arranged such that an index
video signal V.sub.IDX to be recorded is stored into an RAM 22, and
after encoded the signal is recorded on a video tape 2, so that in
the FF/REW mode, the signal is reproduced from the video tape again
and transferred into the RAM 22 again after decoded, and the
address of the RAM 22 is returned to the original address as a
display memory, thereby reproducing a still picture.
On the other hand, the second embodiment is arranged such that the
index video signal V.sub.IDX data stored in the RAM 22 are not
passed through the course of the encoder portion 25, the modulator
portion 26, the stationary head 3, the demodulator portion 27 and
the decoder portion 28 (in other words, without moving the data on
the RAM 22 at all) so that the index video signal V.sub.IDX data
stored in the RAM 22 are used as they are for scale-down display.
This is realized by using the RAM 22 commonly for the double
purpose of writing the index video signal V.sub.IDX data and
reading the data from the RAM 22 as a display memory and by
providing the same relation in the addresses.
The limitation in competition of access between the writing and the
reading still remains. If specific consideration is not given,
access for scale-down display cannot be made in the field period in
which the index video signal V.sub.IDX is stored. However, this
brings about no functional disorder, specifically.
The objects of the second embodiment are in the following
points.
(i) When the mode of the VTR is changed from the REC mode to the
pause or stop, one scene of the video signal (recording video)
immediately before the change of mode is stored as the index video
signal V.sub.IDX in the RAM 22, so that the scale-down display of
the index video signal V.sub.IDX is continuously made during the
pause or stop period. In short, still picture display is made.
(ii) When the mode of the VTR is changed from the ordinary
reproducing mode (PB mode) to the stop mode, one scene of the video
signal (reproducing video) immediately before the change of mode is
stored as the index video signal V.sub.IDX in the RAM 22, so that
the scale-down display of the index video signal V.sub.IDX is
continuously made during the period of the stop mode.
In short, in this embodiment, scale-down display is not made in the
REC or ordinary reproducing mode PB, and one-field still picture
storage (with no display) is executed when the mode of the VT is
changed from the aforementioned mode to the mode in which the
running of the tape stops, whereafter the state of display is
switched to the state of scale-down display. The video output in
the state in which the running of the tape stops is a selected
input signal (the aforementioned line input, tuner input or all
blue) and the contents of the video signal are progressed if any
input exists. In the conventional VTR, what the last scene in the
REC is or where the tape is stopped in the ordinary reproducing
mode PB must be known by human memory or actual reproduction of the
tape. According to the present invention, the recording scene or
reproducing scene at the point where the tape is stopped is stored
as a still picture and inserted as a scale-down display in the
recording video signal. Accordingly, the picture at the current
position of the stopping tape can be displayed to facilitate the
handling of the VTR to shift the necessary mode soon. In
particular, in the case of edition recording, the end scene of the
recording tape can be displayed. Accordingly, the state of
connection with a scene to be recorded after the end scene can be
confirmed by one TV display to facilitate the edition
recording.
When the aforementioned function is combined with the still picture
display (the first embodiment) in the FF/REW operation, a function
that "when the output video scene of the VTR is different from the
scene at the current position of the tape, the scene at the current
position of the tape can be displayed as a scale-down scene" is
attained.
In the prior art, the output video of the VTR does not accord with
the contents of the tape, except (1) during the REC operation and
(2) during the PB operation containing special reproduction.
According to this embodiment, the contents of the tape at the
current position of the tape can be always displayed as a picture
in all the operations of the VTR (even in the state of the running
of the tape) with no special operation.
Accordingly, the picture contents at the current position of the
tape can be always seen with no change of the handling properties
of the conventional VTR. Furthermore, searching through the picture
in the FF/REW operation can be attained though the searching is
impossible in the prior art. Consequently, a large effect and
improvement can be attained in that connection in the contents of
the tape can be confirmed by eyes during the edition of the
tape.
APPLIED EXAMPLE
Although the aforementioned embodiments have been shown as examples
of the present invention, it is to be understood that the present
invention is not limited to those specific embodiments thereof and
that all changes and modifications may be made in the present
invention without departing from the spirit and scope thereof.
In the following, applied examples of the present invention are
disclosed.
Construction and the Like
As described above, the present invention is not limited by the
format of the VTR. The invention can be applied to the case where
the format of the VTR is out of the VHS type as long as a
stationary head can be used.
It is to be understood that the block diagram shown in FIG. 1 may
be divided or integrated suitably as long as the same function can
be attained, and that either analog processing or digital
processing may be used. Further, in the case where digital
processing is used, the aforementioned procedures may be described
by software of a computer (micro-computer) and executed by the
computer.
In particular, the modulator portion 26, the demodulator portion
27, the encoder portion 25 and the decoder portion 28 can be used
sufficiently (though transmission bit rate is related) if the
computer is constituted by a micro-processor capable of executing
relatively high-speed processing.
The A/D converter portion 19 and the writing control circuit 21,
and the D/A converter portion 30 and the reading control portion
29, inclusive of the RAM 22, may be replaced by a conventional,
so-called picture-in-picture apparatus, because the aforementioned
scale-down scene insertion and display method is allied to that
used in the conventional picture-in-picture apparatus. In this
case, the arrangement of picture elements cannot be determined
freely. Of course, the VTR according to the present invention can
be reconstructed so that the function according to the present
invention is added to the picture-in-picture function. In the case
where the VTR according to the present invention is reconstructed
based on the conventional picture-in-picture circuit, the VTR is
reconstructed so that data transfer between the added encoder, the
decoder and the RAM can be executed smoothly with no competition of
access to the RAM for the conventional picture fetching and
display.
Modulation/Demodulation
In the aforementioned embodiment, data are superposed on the CTL
signal by the change of the duty ratio. Although the embodiment has
shown the case where three kinds of duty ratios, data "0", data "1"
and synchronizing, are defined, the present invention can be
applied to the case where four or more kinds of duty ratios may be
defined. Assuming that four-value data (0, 1, 2, 3) are used, then
data of 2 bits can be placed on one frame (one CTL) to increase
transmission rate by twice. Of course, when eight-value data are
used, data of 3 bits can be placed on one frame. However, the width
of the change of the duty ratio decreases as duties increases in
kind, so that difficulty increases for the purpose of demodulating
correct data according to the change of the tap speed.
Although amplitude modulation is not impossible, a risk of
interfering the original CTL increases in the case of amplitude
modulation.
If stationary head tracks other than the control track can be used,
the transmission bit rate (the quantity of information) can be
increased greatly. Although audio based on the stationary head is
essential as "normal audio", VTRs mounting "Hi-Fi audio" based on
FM have been popularized and the fact that the necessity of normal
audio is lowered is undeniable. If there is a thought that the
present invention is used for other purposes, displayed picture
quality can be improved greatly by use of the present invention.
For example, the recording bit rate of about 1 kbit/sec or more can
be realized easily by use of a relatively simple
modulating/demodulating method such as bi-phase modulation. Because
the recording bit rate in the CTL multiplex in this embodiment is
30 bit/sec, the quantity of information is increased by 30 times or
more. As the tape speed changes widely at the time of FF/REW, it is
preferable that a modulating method easy in reproduction of clock
(data delimiter) in demodulation and in sampling of data is used.
Bi-phase modulation is one method which satisfies such a
requirement. Because magnetization is always inverted at each data
delimiter and further inverted in the center of the period of data
"1", data clock can be sampled so easily that digital demodulation
can be constituted easily. The method is suitable for magnetic
recording because the direct- current and low-band contents of
modulated wave are sufficiently small.
Format
In the aforementioned embodiment, CTL multiplex is employed as a
data recording method on the consideration that it is the safest
method. On the contrary, there arises a limitation of data rate. As
described above, the CTL multiplex can be used in practice on the
limitation of the performance level as follows: (1) monochrome, (2)
44.times.45 picture elements, (3) 4 bits per picture element, and
(4) updating period 5 minutes.
However, there is a room for improvement in the aforementioned four
points. Therefore, a method of saving the number of bits to be
transmitted or a method of increasing the transmission bit rate is
required. Of course, the two methods may be used in
combination.
The increase of the transmission bit rate has been described above.
As the quantity of information increased by 30 times or more can be
attained if there is a certain not-CTL multiplex but exclusive
channel, ample improvement in the four points can be attained as
the effect thereof.
Remarkable improvement of the performance, such as (1) color, (2)
192 picture elements (containing color data).times.64 lines, (3) 5
bits per picture element, and (4) updating period 1 minute.
Even in the case of CTL multiplex, the data rate can be increased
by twice with the use of 4-value modulation. In short, the CTL
multiplex can be used for improvement of the performance such as
color, and updating period 3 minutes.
The term "saving the number of bits to be transmitted" means
"high-efficient coding". On the basis of the statistic
characteristic of a picture, bits are concentrated into the
changing portion. For example, data for expressing differential
coding, estimation coding and statistic characteristic are
transmitted. For example, a method of Hadamard transformation has
been known. However, the picture transmitted according to the
present invention is not a moving picture but an individual still
picture. Accordingly, an information quantity compressing method
based on the correlation between frames (fields). The degree of
compression is to be discussed on the consideration of
deterioration of picture quality caused by the compression.
Although the arrangement of recording data obtained by the encoder
is shown in FIG. 2, interleaving means generally used with error
correcting/compensating means are not yet mentioned. As well known,
the effect of correction/compensation can be improved by dispersing
the arrangement of data against concentrated (burst) error in the
transmission line according to a rule so that the burst error can
be dispersed when data are returned to the original arrangement.
Accordingly, the judgment whether such interleaving should be used
or not and what change of the arrangement is given is related to
the length of estimated burst error in the transmission line. For
example, in the case of CTL multiplex, the fact that data rate is
low means the fact that recording wavelength on the tape is long.
The probability that reproducing waveform is disordered by a
scratch or the like of the tape is low. Accordingly, the effect of
interleaving is not large. However, in the case where data rate is
increased by borrowing the normal audio track, it is necessary to
pay attention to the fact that the probability of concentration of
error increases as the data rate increases, that is, as the
recording wavelength decreases.
Of course, such thought about interleaving is also necessary for
determining the capacity of error
detection/correction/compensation.
Although the recording data train in the aforementioned embodiment
contains picture element data, synchronizing required for blocking,
address and CRC, an auxiliary data area may be provided to contain
information such as still picture number, recording date, time,
other recording conditions/states, and so on.
Display Form
Although the aforementioned embodiment has shown the case where a
scale-down picture is inserted in the output video signal of the
VTR, it is a matter of course that a picture without reduction of
the scale thereof may be substituted for the output video signal.
In this case, means for indicating the substitution should be
used.
Although the aforementioned embodiment has shown the case where the
scale-down displayed picture is updated in the form of wiping in
downward order at the time of F and updated in upward order at the
time of REW, the present invention is applied to the case where the
picture may be exchanged with a next picture instantaneously after
the next picture is perfected. In this case, the displayed picture
does not change before the picture is exchanged with the next
picture. Accordingly, the quantity of running of the tape cannot be
found as analog quantity, but there arises a merit in that the
display is stable. If the degree of perfection of the picture
currently subjected to processing is indicated by some display, the
analog quantity of running of the tape can be known to some degree.
For example, a bright spot may be displayed in the end (one side of
the picture frame) of the display area so that a corresponding
quantity of running of the tape in the unit of one still picture
can be known by the movement of the position of the bright
spot.
Although the aforementioned embodiment has shown the case where one
scale-down picture is inserted and displayed, the present invention
can be applied to the case where a plurality of scale-down display
areas may be provided. In this case, the process of the displayed
picture can be known by the plurality of pictures through the step
of successively moving the area where the displayed picture is
updated corresponding to the running of the tape.
Further, the area where updating is made may be set in an end area
in the plurality of areas so that the pictures in the respective
areas are successively shifted with the updating. In this case, a
newest picture can be always displayed in the end area in the
plurality of areas. Because the connection of the areas accords
with the time series of the picture, the process is easy to
understand. Of course, the area where updating is made at the time
of FF and the area where updating is made at the time of REW are
provided opposite to each other in the connection of the display
areas. The display areas may be arranged horizontally or may be
arranged vertically. Of course, the display areas may be arranged
both horizontally and vertically, though the capacity of the RAM
for display and the display reading control of the RAM
increase.
The aforementioned display movement is generally called "scroll".
Although description has been made in the case where the scroll is
made for each picture (area), the present invention can be applied
to the case where such (up and down) scroll may be made more finely
for each line so that the scroll becomes more smooth as an analog
quantity. To scroll the picture laterally, the block of the data
format is constituted by vertically arranged picture elements
rather than laterally arranged picture elements like lines. In
short, the display form sometimes has an influence o the
determination of the data format.
The conventional index or address code may be detected in the mode
of reproducing the still picture in the present invention (FF or
REW mode). As described above, when the VTR portion issues a CTL
recording signal together with index/address information, the
modulator portion 26 and the encoder portion 25 in FIG. 1 defer
their operations and feed the CTL recording signal of the VTR
mechanism 1 directly to the CTL head. Accordingly, the conventional
index/address information can be detected in the CTL signal 16.
In general, the VTR is designed to operate only in the case where
index/address searching is started. However, the still picture
displaying apparatus in the present invention can be constituted so
that a character/symbol for expressing the presence of the
index/address code and a numerical value for expressing the value
of the address are displayed.
In the aforementioned embodiment, one block is constituted by 200
bits. One address code is constituted by 92 bits as shown in FIG.
6(b). In short, the address code is shorter than the block.
Accordingly, even if the index/address code enters into the picture
data, block error is not more than 2 (2 lines). However, about 7
lines must be used in the case where characters (or letters) are
displayed in the display screen. If a number of four figures is
displayed when the index/address code enters into the picture data,
the display is effective for estimation for searching. The index or
characters such as numerical characters can be attained by
transferring a predetermined data pattern onto the RAM 22 based on
information detected by the index/address detecting function of the
demodulator portion 27 and decoder portion 28.
Of course, this function can be used widely for the purpose of
transferring and displaying character/symbol patterns related to
the general operations of the VTR as well as characters/symbols
related to the index/address.
As described above, according to the present invention, an index
video signal to be recorded based on the recording control circuit
is stored as digital-coded data in the RAM, after encoded the
stored signal is recorded on a magnetic tape, the signal is
reproduced from the magnetic tape at the time of FF/REW, and after
decoded the signal is returned to the analog signal again so as to
be outputted in the form of a still picture. Accordingly, searching
in the FF/REW mode can be made exactly, finely and speedily based
on searching reference information which is provided in the form of
a picture as visual data with no special operation for the
searching. Further, the searching is made regardless of the rotary
video head, so that there is no failure of the head caused by the
searching.
* * * * *